Abstract: In order to explore the regulatory mechanism of high voltage electric field (HVEF) on ripening and senescence of postharvest fruit, effects of steady electric field (SEF) or alternative electric field (AEF) treatment on metabolism of active oxygen species in harvested tomato fruits were studied. Results showed that AEF treatment could reduce SOD and CAT activities of tomato fruits on initial periods of storage, delay the increase of SOD activity and decrease of CAT activity on later periods of storage. However, SEF could not significantly increase the SOD or CAT activity. Both SEF or AEF treatments delayed the appearance of POD activity peak. Higher levels of AsA and GSH contents were observed in SEF-treated fruits than those in non-SEF and non-AEF treated fruits. During storage, high electric field treament significantly inhibited the production of H₂O₂ and O·₂- in tomato fruits.